Reactive Electrochemical Membrane Research Articles

Ultra-efficient decontamination via functionalized reactive electrochemical membrane for peroxymonosulfate activation: High water flux with extremely low energy consumption

A perovskite LaCoO3 functionalized Ti4O7 reactive electrochemical membrane (REM) was developed for electro-enhanced peroxymonosulfate (PMS) activation (E-REM-PMS), addressing limitations in wastewater treatment efficiency, reusability, and interference resistance. It achieved 100% carbamazepine (CBZ) removal at a rate constant of 39.69 min−1, 233 and 23 times of electro-REM (E-REM) system without PMS and REM-PMS system without electricity. In-situ Fourier transform infrared spectroscopy (FTIR) highlighted the promotion of electro-activation on PMS, while density functional theory (DFT) calculations elucidated mechanism differences under three adsorption configurations. 1O2 (2.97×10−9 M), SO4•− (2.09×10−11 M) and •OH (7.36×10−12 M) dominated the E-REM-PMS system, consistent with sequence of reactive species by DFT results. Continuous treatment of pharmaceutical wastewater confirmed 100% CBZ removal and 60%-70% TOC mineralization at ultrahigh water flux (642.86 L/m2·h) with minimal energy consumption (0.01 kWh/m3·order). This work proposed a high-performance and anti-fouling REM, offering an efficient and economical solution for wastewater treatment.

Enhanced treatment of p-nitrophenol and coking wastewater through electrochemical and electrochemical-ozonation coupling process utilizing a novel Ti4O7 reactive electrochemical membrane anode

Organic pollutants in water could be removed by electrochemical treatment using a reactive electrochemical membrane (REM) with Magnéli phase Ti4O7, yet it is challenging to design suitable porosity to realize effective mass transfer and enhance the reactivity. Here, a novel Ti4O7 REM was prepared by a spark plasma sintering (SPS) method, which showed excellent electrochemical reactivity and mass transfer rate for organic pollutants in water. Compared to other Ti4O7 REMs, the novel Ti4O7 REM achieved a 140–9000-fold decrease in charge transfer resistance and a 5–110-fold increase in mass transfer rate. The p-nitrophenol in water can be completely removed in the REM system, with a maximum total organic carbon (TOC) removal rate of 85%. Then the REM system obtained an amazing removal rate of TOC (50.1%) and UV254 (89.6%) in the electrochemical treatment of real coking wastewater. In addition, to further enhance the removal efficiency, a coupled oxidation process with the novel Ti4O7 REM and O3 aeration was investigated. The TOC removal rate and energy consumption were 57.1% and 165.2 kWh (kg TOC)−1 at the optimal conditions within a short treating time. Our findings highlighted an innovative REM for a broad range of potential environmental applications.

Enhanced oxidation of organic pollutants by regulating the interior reaction region of reactive electrochemical membranes

Reactive electrochemical membrane (REM) emerges as an attractive strategy for the elimination of refractory organic pollutants that exist in wastewater. However, the limited reaction sites in traditional REMs greatly hinder its practical application. Herein, a feed-through coating methodology was developed to realize the uniform loading of SnO2-Sb catalysts on the interior surface of a REM. The uniformly coated REM (Unif-REM) exhibited 2.4 times higher reaction kinetics (0.29 min–1) than that of surface coated REM (Surf-REM) for the degradation of 2 mM 4-chlorophenol (4-CP), rendering an energy consumption as low as 0.016 kWh gTOC–1. The fast degradation of various emerging contaminants, e.g., sulfamethoxazole (SMX), ofloxacin (OFLX), and tetracycline (TC), also confirms its superior oxidation capability. Besides, the Unif-REM exhibited good performance in generating hydroxyl radicals (•OH) and a relatively long service lifetime. The simulation of spatial current distribution demonstrates that the interior reaction region in the Unif-REM channels can be drastically extended, thereby maximizing the surface coupling of mass diffusion and electron transfer. This study offers an in-depth look at the spatially confined reactions in REM and provides a reference for the design of electrochemical systems with economically efficient water purification.

(Invited) Non-Uniformly Polarized Reactive Electrochemical Membrane (REM) for Water Purification

A novel flow-through electrochemical technology (or termed reactive electrochemical membrane, REM) developed from porous electrode materials has recently attracted increasing attention globally in water purification and environment remediation. REM systems compress the boundary diffusion layer on the surface of the electrode via a combination of the convection of the solution and the constraint effect of the micro-pore structure, thus overcoming the mass transfer limitation in traditional flow-by systems. As a result, the kinetics of contaminant separation and conversion in a REM system increases by several to tens of times as compared with the flow-by systems. However, most existing studies are focused on the development of novel electrode materials, the evaluation of the removal efficiency and mechanism for contaminants, and the optimization of the treatment process of a REM system. In comparison, there is a gap in understanding the working principles of the REM electrodes. In contrast to the traditional flow-by system, the convective transport of the solution in the REM system drives the contaminants to the inside of the REM electrode, which activates the inner catalytic zone thereby. Because the electrode features the characteristics of non-uniform polarization, the given potential decays continuously along the depth of the REM electrode, thus causing a non-uniform distribution of the potential inside the REM electrode. As such, the zero-dimensional reaction theory of the electrode in traditional flow-by system (that is, the reaction mainly occurs on the surface of the electrode and is controlled by the potential) is no longer applicable to REM electrodes. It is therefore vital to revisit the reaction mechanism of the REM electrode. This Presentation therefore discusses the non-uniform polarization characteristics of the REM electrodes that are developed by loading catalytic layer on porous substrates. The main contents include: (1) REM electrode d emonstrates non-uniform oxidation characteristics: The key influencing factors ( i.e. , the pore structure of the REM electrode and the concentration of the electrolyte) and their principles of action to determine the reaction depth of a REM electrode have been identified, by employing (1) a developed mathematical model that could describe the spatial overpotential distribution as a function of depth in the REM electrode and (2) a visualization method to characterize the reactive depth of a REM electrode. (2) There is a structure-function relationship between the REM electrode pore structure and water purification efficiency : A series of SnO2-Sb-REMs with pore diameters in a range of 4.7 to 49.4 μm have been prepared to study the influence of the key factor ( i.e. , pore structure) on the transport-oxidation process of typical antibiotics. The REM electrode performance that could not constantly increase with a decrease in the pore diameter relates to the decreasing reactive depth of the electrode at a smaller pore diameter, which would lead to the compromise of the intrinsic kinetics of a REM electrode. (3) Direct electron transfer (DET) dominates the oxidation of antibiotics by using REM developed from porous substrates with a catalytic layer: The mechanism of typical antibiotics removal by employing SnO2-Sb-REM, β -PbO2-Sb-REM and Ti4O7-REM has been systematically investigated. The non-uniform oxidation characteristics of the REM electrode resulted in the DET rate being much higher than the yield of the hydroxyl radical (•OH), which was insignificantly affected by the electrode materials. The strong DET ability enabled the REM system to quickly and efficiently degrade antibiotics, which also imparted the REM system a stronger resistance to the background matrix (such as Cl–, HCO3 – and natural soluble organic matter).

Electrochemical oxidation of reverse osmosis concentrate using a pilot-scale reactive electrochemical membrane filtration system: Performance and mechanisms

Scale-up treatment of real wastewater holds the key to promoting the practical application of electrochemical filtration technology. This work used a pilot-scale Ti/Pd reactive electrochemical membrane (REM) system (12 REM modules with a total REM area of 0.144 m2) to treat high-salinity reverse osmosis concentrate (ROC) from a chemical industry park. The pilot-scale Ti/Pd REM system demonstrated effective electrochemical degradation of ROC wastewater, achieving removal efficiencies of 82.3 ± 1.9% for COD and 46.7 ± 5.6% for TN at a membrane flux of 90 L/(m2·h) and a cell voltage of 5 V, with an energy consumption of 0.045 kWh/g-COD. Singlet oxygen (1O2) and reactive chlorine species were identified as the two primary reactive oxygen species generated in the Ti/Pd REM system. Fluorescence spectroscopy and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) analysis indicated that the pilot-scale Ti/Pd REM treatment effectively oxidized humic acid-like substance and unsaturated aromatic compounds. Overall, the Ti/Pd REM technology shows a promising application potential for the treatment of high-salinity ROC from the chemical industry.

Development of Ti4O7 reactive electrochemical membrane and electrochemical oxidation of naphthols in aqueous solution

Naphthols (NAPs), commonly used phenolic compounds, have significant impact on environmental risk and human health, necessitating advanced treatment methods for their degradation. In this study, a Ti4O7 reactive electrochemical membrane (REM) was developed for the electrochemical oxidation of NAPs. The Ti4O7 REM presented a porosity of 42.18 ± 2.3% and a median pore diameter of 1.21 µm. High permeability (846 LMH bar−1) was achieved at relatively low transmembrane pressure and resulted in a convection-enhanced rate constant for Fe (CN)64- oxidation of 1.7 × 10−4 m/s. The increase in current density and decrease in plate spacing had a positive influence on NAPs degradation. The TOC removal efficiencies of 1-naphthol (1-NAP) and 2-naphthol (2-NAP) were 68.6% and 63.5%, respectively at the current density of 6 mA/cm2 and plate spacing of 10 mm. Additionally, quantum chemical calculation using density functional theory (DFT) was employed to identify the active sites of NAPs through atom charge and frontier electron density (FED) calculations. Results showed that C14 and C10 were identified as the active sites for 1-NAP, while C9 and C13 were the active sites for 2-NAP. Hydroxyl radical and sulfate radical produced on the electrode surface were the main oxidants for NAPs degradation during the electro-oxidation process. The degradation pathway included hydroxylation, oxygenation, decarbonylation, and ring-open processes, which was in agreement with the theoretical calculations. Furthermore, the quantitative structure-activity relationship (QSAR) predictive model was used to assess the toxicity changes during the electrochemical oxidation process of NAPs, suggesting that the toxicity of intermediates increased at the beginning and significantly reduced at the end. This comprehensive study provides practical and theoretical insights into the application of electrochemical oxidation technique for the reduction of refractory compounds in wastewater.

Electrochemical treatment of municipal reverse osmosis concentrates by a TiO2-BNTs/SnO2-Sb reactive electrochemical membrane

With the wide application of reverse osmosis technology in municipal wastewater treatment, the abundance of generated reverse osmosis concentrates (ROC) has become a significant challenge for water ecosystems. In this work, a fabricated TiO2-BNTs/SnO2-Sb reactive electrochemical membrane (REM) was used to dispose of municipal ROC wastewater. The effects of the TiO2 nanotube array (TiO2-BNTs) interlayer, current density, initial pH and flow rate on the COD removal of ROC were investigated. In addition, the 3D-EEM fluorescence spectra showed that humic acid-like substances and soluble microbial byproduct-like substances could be removed effectively. GC-MS analysis indicated that most organics, including aldehydes, phenols, ethers, nitriles, ketones, silanes and alcohols, were eliminated after treatment. The REM also exhibited prominent membrane anti-fouling performance in high-salinity wastewater. After 20 cycles, the transmembrane pressure (TMP) was only slightly changed (within 3 kPa) compared to that of the first cycle. Two key parameters, i.e., service lifetime and energy consumption, were investigated in ROC treatment. The service lifetime reached 31350 h (3.5 years, 20 mA cm−2) in 0.5 M NaCl solution and 40390 h (20 mA cm−2, 4.6 years) in actual wastewater, which is highly competitive with previously reported electrodes. Energy consumption reached 10.5 kWh·kg COD−1 in actual ROC wastewater, which is more acceptable compared with current reported electrochemical technologies and exhibits great application prospects for TiO2-BNTs/SnO2-Sb REMs.

Electrooxidation of chlorophene and dichlorophen by reactive electrochemical membrane: Key determining factors of removal efficiency

This study systematically investigated the variable main electrooxidation mechanism of chlorophene (CP) and dichlorophen (DCP) with the change of reaction conditions at Ti4O7 anode operated in batch and reactive electrochemical membrane (REM) modes. Significant degradation of CP and DCP was observed, that is, CP exhibited greater removal efficiency in batch mode at 0.5–3.5 mA cm−2 and REM operation (0.5 mA cm−2) with a permeate flow rate of 0.85 cm min−1 under the same reaction conditions, while DCP exhibited a faster degradation rate with the increase of current density in REM operation. Density functional theory (DFT) simulation and electrochemical performance tests indicated that the electrooxidation efficiency of CP and DCP in batch mode was primarily affected by the mass transfer rates. And the removal efficiency when anodic potentials were less than 1.7 V vs SHE in REM operation was determined by the activation energy for direct electron transfer (DET) reaction, however, the adsorption function of CP and DCP on the Ti4O7 anode became a dominant factor in determining the degradation efficiency with the further increase of anodic potential due to the disappeared activation barrier. In addition, the degradation pathways of CP and DCP were proposed according to intermediate products identification and frontier electron densities (FEDs) calculation, the acute toxicity of CP and DCP were also effectively decreased during both batch and REM operations.

Preparation of Ti4O7 Reactive Electrochemical Membrane for Electrochemical Oxidation of Coking Wastewater

The effluent of coking wastewater comprises hundreds of refractory organics and is characterized by high toxicity and non-biodegradation. Electrochemical advanced oxidation processes (EAOPs) have been widely applied in the field of water purification. In this study, a Ti4O7 reactive electrochemical membrane (REM) was prepared using the plasma spraying method for the electro-oxidation of coking wastewater. The composition and surface morphology of the Ti4O7 REM were characterized via X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The computational fluid dynamics (CFD) simulation was used to compare the mass transfer performance of the Ti4O7 REM in traditional batch (TB) mode and flow-through (FT) mode. In the FT mode, the effects of current density and anode–cathode distance on the treatment efficiency were investigated, and the electrocatalytic performance of the anode on coking wastewater was analyzed. The results showed that the COD removal efficiency reached 76.2% with an energy consumption of 110.5 kWh kg−1 COD under the optimal condition. In addition, cathodic polarization provides an effective technique for maintaining the long-term activity of the Ti4O7 REM. The three-dimensional fluorescence results and UV-vis spectrum showed that the aromatic compounds could be effectively degraded using the Ti4O7 REM. The Ti4O7 REM demonstrated excellent performance of electrochemical oxidation and satisfactory stability, which had a strong potential for application in the field of practical wastewater and engineering practices that respond to the concept of sustainable development.

Unveiling the spatially confined oxidation processes in reactive electrochemical membranes

Electrocatalytic oxidation offers opportunities for sustainable environmental remediation, but it is often hampered by the slow mass transfer and short lives of electro-generated radicals. Here, we achieve a four times higher kinetic constant (18.9 min−1) for the oxidation of 4-chlorophenol on the reactive electrochemical membrane by reducing the pore size from 105 to 7 μm, with the predominate mechanism shifting from hydroxyl radical oxidation to direct electron transfer. More interestingly, such an enhancement effect is largely dependent on the molecular structure and its sensitivity to the direct electron transfer process. The spatial distributions of reactant and hydroxyl radicals are visualized via multiphysics simulation, revealing the compressed diffusion layer and restricted hydroxyl radical generation in the microchannels. This study demonstrates that both the reaction kinetics and the electron transfer pathway can be effectively regulated by the spatial confinement effect, which sheds light on the design of cost-effective electrochemical platforms for water purification and chemical synthesis.

Can perfluorooctanoic acid be effectively degraded using β-PbO2 reactive electrochemical membrane?

Aqueous perfluorooctanoic acid (PFOA) elimination has raised significant concerns due to its persistence and bioaccumulation. Although β-PbO2 plate anodes have shown efficient mineralization of PFOA, it remains unclear whether PFOA can be effectively degraded using β-PbO2 reactive electrochemical membrane (REM). Herein, we assessed the performance of Ti/SnO2-Sb/La-PbO2 REM for PFOA removal and proposed a possible degradation mechanism. At a current density of 10 mA/cm2 and a membrane flux of 8500 (liters per square meter per hour, LMH), the degradation efficiency of 10 mg/L PFOA was merely 8.8%, whereas the degradation efficiency of 0.1 mg/L PFOA increased to 96.6%. Although the porous structure of the β-PbO2 REM provided numerous electroactive sites for PFOA, the generated oxygen bubbles in the pores could block the pore channels and adsorb PFOA molecules. These hindered the protonation process and significantly impeded the degradation of high-concentration PFOA. Quenching experiments indicated that •OH played dominant role in PFOA degradation. The electrical energy per order to remove 0.1 mg/L PFOA was merely 0.74 Wh/L, which was almost an order of magnitude lower than that of other anode materials. This study presents fresh opportunities for the electrochemical degradation of low-concentration PFOA using β-PbO2 REM.

Reactive electrochemical ceramic membrane filtration system for efficient treatment of enrofloxacin from wastewater: Mechanisms and applications

Reactive electrochemical ceramic membrane filtration system for efficient treatment of enrofloxacin from wastewater: Mechanisms and applications

Degradation of 17β-estradiol and antifouling properties of magnéli phase Ti4O7 reactive electrochemical membrane in the presence of fulvic acid

This study systematically investigated the electrooxidation of 17β-estradiol (E2) and inhibition of formation of fulvic acid (FA) aggregation in reactive electrochemical membrane (REM) made of Ti4O7. Our results indicate that aggregated FA in the membrane could retard the breakthrough rate of E2, while the interception for E2 was significantly alleviated for treated FA due to its structural change during REM electrooxidation. The electrooxidation removal efficiency of E2 during REM operation increased with the decrease of permeate flow rates due to the longer residence time within REM, and 95.90 ± 0.92% removal was reached at 20 mA cm−2 with the permeate flow rate of 7.5 mL min−1. FA inhibited the electrooxidation of E2 accompanied by the generation of specific intermediate products. Our results involving designed experiments and molecular simulation calculation indicated that direct electron transfer (DET) reaction induced polymer generation, and the generation of hydroxylation and ring-opening products was initiated by the reaction with hydroxyl radicals (•OH). Permeate flux analysis and excitation-emission matrix characterization indicated that significant antifouling performance of REM was mainly attributed to the structural change of FA during REM treatment. These results revealed the potential roles of natural organic matter in Ti4O7 REM treatment of organic contaminants that greatly promoted the development of REM operation application.

Electrochemical activation of peroxymonosulfate using chlorella biochar modified flat ceramic membrane cathode for berberine removal: Role of superoxide radical and mechanism insight

Both the low-cost biomass biochar and reactive electrochemical membrane (REM) have been proved as a feasible method for persulfate electro-activation. However, the biochar modified REM, especially be use as cathode for persulfate activation, was rarely reported. To this end, the electro-activation of peroxymonosulfate (PMS) for treating berberine hydrochloride (BH) was performed by a novel polyacrylonitrile cross-linked chlorella biochar (CBC-700) modified flat ceramic membrane (FCM) cathode. Results revealed that the applied electric field, CBC-700/FCM and PMS establish an excellent synergetic effect in the CBC-700/FCM + PMS integrated electrocatalytic oxidation-filtration system. High graphitizing and N-doping defect degree of CBC-700/FCM facilitate PMS electro-activation. Reactive species quenching and EPR experiments demonstrated the co-generation of OH, SO4∙- and 1O2, while 1O2 formed with O2∙-/HO2- as the crucial precursor provided more contribution (52.6%) to BH removal. The tolerance experiments against inorganic anions, humic acid and different water matrixes affirmed the excellent anti-membrane fouling ability and the practical applicability of CBC-700/FCM. Finally, the degradation pathways of BH was also proposed based on the results of LC/MS.

Carbon electrochemical membrane functionalized with flower cluster-like FeOOH catalyst for organic pollutants decontamination

Decorating active catalysts on the reactive electrochemical membrane (REM) is an effective way to further improve its decontamination performance. In this work, a novel carbon electrochemical membrane (FCM-30) was prepared through coating FeOOH nano catalyst on a low-cost coal-based carbon membrane (CM) through facile and green electrochemical deposition. Structural characterizations demonstrated that the FeOOH catalyst was successfully coated on CM, and it grew into a flower cluster-like morphology with abundant active sites when the deposition time was 30 min. The nano FeOOH flower clusters can obviously boost the hydrophilicity and electrochemical performance of FCM-30, which enhance its permeability and bisphenol A (BPA) removal efficiency during the electrochemical treatment. Effects of applied voltages, flow rates, electrolyte concentrations and water matrixes on BPA removal efficiency were investigated systematically. Under the operation condition of 2.0 V applied voltage and 2.0 mL·min−1 flow rate, FCM-30 can achieve the high removal efficiency of 93.24% and 82.71% for BPA and chemical oxygen demand (COD) (71.01% and 54.89% for CM), respectively, with only a low energy consumption (EC) of 0.41 kWh·kgCOD-1, which can be ascribed to the enhancement on OH yield and direct oxidation ability by the FeOOH catalyst. Moreover, this treatment system also exhibits good reusability and can be adopted on different water background as well as different pollutants.

Electrochemical activation of peroxymonosulfate by 3D printed blue TiO2 nanotube arrays reactive electrochemical membrane for efficient degradation of acetaminophen

Electrocatalytic technology (EC) is a promising strategy for peroxymonosulfate (PMS) activation due to its environmental safety and energy conservation. Herein, 3D printed blue TiO2 nanotube arrays (3DP-BTNAs) reactive electrochemical membranes (REM) were designed as anode and cathode in EC and EC/PMS systems. EC/PMS system displayed superior performance for acetaminophen (ACT) degradation and detoxication. The ACT degradation in EC/PMS system was 3.70 times faster than that in EC system. Quenching experiments suggested that singlet oxygen (1O2) mediated nonradical pathway was responsible for ACT degradation in EC/PMS system, while hydroxyl radical (•OH) was the predominant reactive oxygen species (ROS) in EC system. Our study first provided direct evidence that PMS activation on cathode was mainly triggered by superoxide radical (O2•-). PMS was reduced by O2•- derived from O2 reduction on cathode, and subsequently converted into ROS for organics oxidation. However, PMS tended to adsorb on anode and formed 3DP-BTNAs-PMS* complex for organics degradation. The influencing factors (e.g., PMS dosage, flow rate) on ACT degradation in EC/PMS system were evaluated, and the obtained optimal kinetic constant and lowest energy consumption were 0.135 min−1 and 0.27 Wh/L, respectively. In addition, eight degradation products were identified and possible degradation pathways of ACT were proposed to be the cleavage of C-N bonds and benzene ring. This study is dedicated to the rational design of highly porous REM material by 3DP technology for wastewater treatment and the in-depth mechanism of PMS activation over BTNAs electrode in EC/PMS system.

Electrochemical oxidation of bio-treated landfill leachate using a novel dynamic reactive electrochemical membrane (DREM)

Bio-treated landfill leachate contains complex refractory organics, which lead to short membrane life for subsequent membrane processes. In this work, a blue TiO2 nanotubes (TiO2-BNTs) reactive electrochemical membrane combined with dynamic SnO2-Sb magnetic composite particles (MCPs), i.e., dynamic reactive electrochemical membrane (DREM) technology, was developed to enhance contaminant removal and improve antifouling performance under harsh water quality. A 98% removal of ammonia as well as 67% and 78% reduction in nitrate and total nitrogen were achieved, respectively. An increase of nearly 45% and 20% COD removal in a 2.0 g MCP-loaded DREM was found upon a 0 g MCP-loaded DREM and static TiO2-BNTs/SnO2-Sb membrane electrode (SREM), respectively. The synergetic mechanism revealed the inner dynamic MCP layer (adjacent to TiO2-BNTs surface) played a key role in organic degradation, and the outer layer (adjacent to bulk solution) acted as a protective layer to diminish fouling. Additionally, DREM provided a more optimized distribution and effective usage for reactive oxygen species (ROS). A high and stable COD removal of > 75% was confirmed in repeated experiments. A > 24% lower energy consumption was found with the DREM compared with other electrochemical technologies, which proved the DREM is a viable method for practical applications.

Environment-friendly and efficient electrochemical degradation of sulfamethoxazole using reduced TiO2 nanotube arrays-based Ti membrane coated with Sb-SnO2

This study focused on the preparation, characterization, and sulfamethoxazole (SMX) removal performance of the SnO2-coated reactive electrochemical membrane (REM). This REM was fabricated by loading SnO2 on the reduced TiO2 nanotube arrays (RTNA)-based Ti membrane (TM). Regarding the dopant for SnO2, Sb was more effective in boosting the electrocatalytic activity than Bi, and the energy consumption for Sb-SnO2-coated REM (TM/RTNA/ATO) was lower than Bi-SnO2-coated REM (TM/RTNA/BTO). As for the internal layer, RTNA provided TM/RTNA/ATO with more electroactive surface areas and prolonged the service lifetime. Compared with batch mode, the SMX removal efficiency in flow-through mode was increased up to 8.4-fold. The SMX degradation performances were also affected by fluid velocity, current density, initial SMX concentration, and electrolyte concentration. The synergistic effects of •OH oxidation and direct electron transfer were responsible for the effective removal of SMX. TM/RTNA/ATO was proved to be stable and durable by multi-cycle and accelerated lifetime tests. Its extensive applicability was verified with high removal efficiencies of SMX in the surface water and wastewater effluent. These results demonstrate the promise of TM/RTNA/ATO for water treatment applications.

Enhanced degradation mechanism of anticancer drug irinotecan through low-frequency ultrasound assisted reactive electrochemical membrane

The effect of low-frequency ultrasound (US, 20 kHz, 104 W) on the degradation of anticancer drug irinotecan (IRI) using reactive electrochemical membrane (REM) was investigated. Results demonstrated that higher k value (0.103 min−1) and mineralization efficiency (94.6%) as well as lower energy consumption (0.906 Wh L−1) were observed in US-REM system. The effects of influence factors including US power, volume flow rate, current density and initial IRI concentration on the degradation of IRI were studied in US-REM system. The relative contributions of •OH, SO4•− and O2•− (indirect oxidation) to IRI degradation using REM were all increased with the assistance of US. The production rate of •OH using US-REM increased by 19.7% compared with that using REM. Seven intermediates of IRI degradation using both REM and US-REM were identified, and the main degradation pathways of IRI were hydroxylation, oxidation and ring cleavage. The enhanced degradation and mineralization of IRI in US-REM system could mainly be attributed to higher •OH production and higher contribution of free radicals.

Energy-efficient removal of trace antibiotics from low-conductivity water using a Ti4O7 reactive electrochemical ceramic membrane: Matrix effects and implications for byproduct formation

The inevitably high energy consumption of traditional electrochemical processes to treat low-conductivity water has limited their wider application. Herein, we present an energy-efficient alternative, i.e., a Ti4O7 reactive electrochemical ceramic membrane (Ti4O7-REM) system with a superior mass transfer ability. For the removal of 10−200 μM norfloxacin (NOR) from low-conductivity (178−832 μS cm−1) water, the Ti4O7-REM system increased the kinetics rate constant by 4.3−34.0 times, thus decreasing the energy cost by 80.5−97.3% compared with a flow-by system. The rapid NOR removal was related to the enhanced direct electron transfer process in the Ti4O7-REM system, which allowed for higher resistance to HCO3− scavenging and a favorable reaction between NOR and the active sites. Meanwhile, this mechanism likely contributed to the less formation of inorganic chlorinated product, ClO3−, in the presence of Cl−. Although organic chlorinated byproducts were not detected during NOR degradation in the Ti4O7-REM system, Cl– influenced the speciation of the intermediates. A single-pass Ti4O7-REM system demonstrated 94−97% removal of trace antibiotics from real water samples in 30 s. The additional energy consumption (<0.02 kWh m−3) using a Ti4O7-REM system only contributed to 5.0−6.4% of the total in a typical tertiary wastewater treatment plant. Based on the above results, we can conclude that the convection-enhanced REM technique is viable for the purification of low-conductivity natural waters.